Biological membranes are described as a mosaic of different domains where interactions between membrane
components induce the formation of subdomains with different characteristics and functions. Lipids play an
important role in the formation of lipid-enriched microdomains where they dynamically associate to form platforms
important for membrane protein sorting and construction of signaling complexes. Cholesterol confi ned
in lipid domains is a crucial component required by microorganisms, directly or indirectly, to enter or exit the
intracellular compartment. Cellular activation mediated by superfi cial bacterial component may be modifi ed by
local cholesterol depletion. Therefore, new perspectives for unconventional therapeutic intervention in Gramnegative
infections may be envisaged. We tested this hypothesis by using methyl-β-cyclodextrin (mβCD) as a
cholesterol-complexing agent to alter the U937 plasma membrane cholesterol content. Our results demonstrate
that cholesterol depletion of U937 cells inhibited Salmonella enterica serovar Typhimurium porins-mediated phosphorylation
of Src kinase family, protein kinase C (PKC), JNK, and p38, while cholesterol repletion restored the
phosphorylation. Lipopolysaccharide (LPS) extracted from the same bacterial strain has been used as a control.
Our data demonstrate that the lack of activation of signal transduction pathway observed following cholesterol
depletion differently modulates the release of interleukin-6 (IL-6) or tumor necrosis factor-α (TNF-α), suggesting
that Src, associated to lipid domains, may represent an important pathway in Gram-negative-induced cellular
signal.

Biological membranes are described as a mosaic of different domains where interactions between membrane
components induce the formation of subdomains with different characteristics and functions. Lipids play an
important role in the formation of lipid-enriched microdomains where they dynamically associate to form platforms
important for membrane protein sorting and construction of signaling complexes. Cholesterol confi ned
in lipid domains is a crucial component required by microorganisms, directly or indirectly, to enter or exit the
intracellular compartment. Cellular activation mediated by superfi cial bacterial component may be modifi ed by
local cholesterol depletion. Therefore, new perspectives for unconventional therapeutic intervention in Gramnegative
infections may be envisaged. We tested this hypothesis by using methyl-β-cyclodextrin (mβCD) as a
cholesterol-complexing agent to alter the U937 plasma membrane cholesterol content. Our results demonstrate
that cholesterol depletion of U937 cells inhibited Salmonella enterica serovar Typhimurium porins-mediated phosphorylation
of Src kinase family, protein kinase C (PKC), JNK, and p38, while cholesterol repletion restored the
phosphorylation. Lipopolysaccharide (LPS) extracted from the same bacterial strain has been used as a control.
Our data demonstrate that the lack of activation of signal transduction pathway observed following cholesterol
depletion differently modulates the release of interleukin-6 (IL-6) or tumor necrosis factor-α (TNF-α), suggesting
that Src, associated to lipid domains, may represent an important pathway in Gram-negative-induced cellular
signal.